1. Field of the Invention
The invention relates to a braking control apparatus and braking control method for a vehicle, which control a regenerative braking force and a hydraulic braking force on the basis of a required braking force according to a brake operation amount.
2. Description of Related Art
Japanese Patent Application Publication No. 2010-215084 (JP 2010-215084 A) describes one example of a so-called by-wire hydraulic braking system. In such a hydraulic braking system, a master cylinder in which hydraulic pressure is generated in accordance with a brake operation amount is separated from each of wheel cylinders respectively provided in wheels. Therefore, when a hydraulic pressure in each wheel cylinder is increased on the basis of driver's brake operation, brake fluid in an amount appropriate to a required hydraulic braking force is supplied into each wheel cylinder through operations of pumps or valves. Thus, the hydraulic pressure in each wheel cylinder, that is, the hydraulic braking force appropriate to the required hydraulic braking force, is imparted to a vehicle.
Such a hydraulic braking system may be provided in a vehicle including a drive motor that is one example of a drive regeneration imparting device that is able to impart regenerative braking force. For example, in such a vehicle, a required braking force according to a driver's brake operation amount is computed, and it is determined whether the regenerative braking force that is being imparted to the vehicle by the drive motor is smaller than the required braking force. When the regenerative braking force is smaller than the required braking force, a required hydraulic braking force is computed in accordance with a difference obtained by subtracting the regenerative braking force from the required braking force, and the hydraulic braking system is controlled so that the hydraulic braking force is brought close to the required hydraulic braking force.
As described above, in the hydraulic braking system that adjusts the braking force of the vehicle as a whole in cooperation with the drive motor, a computing process of computing a required hydraulic braking force is executed by a controller, and then the hydraulic braking system is operated in order to bring the hydraulic braking force close to the required hydraulic braking force that is the result of the computing process. Therefore, the response speed of the hydraulic braking force decreases for the necessity of such a computing process, so there is a concern that drivability decreases. That is, in reducing the hydraulic braking force on the basis of a reduction in driver's brake operation amount, the start of reduction in the hydraulic braking force delays, so the deceleration of the vehicle is difficult to decrease.